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Cultivating better practice

28 September 2016

Most potato growers could afford to cultivate at least one inch shallower, according to NIAB research scientist, Mark Stalham, who outlined the benefits of reduced cultivation at the latest AHDB SPot Farm walk.

The event, held at James Daw’s farm in Staffordshire, identified reduced erosion, better work speeds and reduced costs as just some of the advantages associated with limiting secondary cultivation depth and intensity. All of which can be achieved without suffering a yield hit, according to Dr Stalham.

Bed forming, bed tilling and destoning were all recognised as potential secondary operations.

The trials build on around 80 experiments which have been carried out over the past five years as part of an AHDB project, all of which have shown a benefit from reducing tillage depth. Moreover, every farmer involved in the project has since reduced their standard depth of cultivation.

Dr Stalham said: “By doing secondary cultivations less intensively, shallower or by removing an operation, we can actually improve yields, maintain crop quality and be able to harvest with minimal damage, without reducing planting depths.

“Typically, everybody could afford to go about an inch shallower, but many people could actually double that and have no loss in performance but instead could gain an advantage.”

In doing so, he suggested the cost of machines, labour and fuel could be cut.

In fact, this season’s SPot Farm results indicate that where primary cultivations where reduced by 5cm and where the bed-tilling operations were removed, the total cost of fuel and labour dropped by 46 per cent across all soil types.

Additionally, overall yield increased consistently across a number of cultivation methods, with the highest yield of 71.1t/ha (28.7t/acre) being achieved where a heavy Simba SL was used followed by shallow secondary operations.

Shallow cultivations - the theory

Throughout the project, where shallower cultivations have been adopted, the resulting ridge has been much smaller and the soil particles, much closer together.

 Dr Stalham said: “If we work the soil shallower and we perhaps remove the bed-tilling operation on heavier soils, we find the ridge tends to be smaller and denser.

 “As a consequence, it is more stable to changes in soil weathering that we get for the next five months of its life and so the ridge profile largely stays where it is.”

 While many growers aim for a fine soil tilth in an attempt to retain soil moisture around the tuber, partly to prevent common scab, Dr Stalham suggested that some growers had gone too far.

 “Soil in a potato ridge tends to get finer so if you start with a soil that is cloddy, it will tend to get less cloddy as the season progresses.

“When you have a very porous, open structure with large clods, yes the risk of common scab is increased as you can’t contain that film of water around the tubers, but very few growers actually have a seedbed so coarse.

 “In fact, currently soils are much finer than we need to achieve in terms of producing adequate skin quality.”

Dr Stalham also discussed the loss of porosity and soil structure following heavy rainfall events where soils have been over-cultivated.

“If we over cultivate soils, we end up with a soil that is really prone to slumping at the beginning of the season and if it rains we get poor seedbeds as a consequence,” he said.

Source: FG Insight

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